In various cigarette filters, a pair of end filter plug members are encircled by filter wrap and therewith define a cavity for containment of a measured quantity of low-density granular material between the plug members. Typically, the flow characteristics, of the granular material are such that positive, i.e., forcible transfer thereof is required. Thus, the material is frequently not free-flowing and gravity, air pressure, mechanical force or other positive assist is employed in transfer thereof.
In granular material transfer arrangements heretofore known for use in filter cigarette manufacture, such as are shown in U.S. Pats. Nos. 3,545,345 and 3,550,508, rotative members define peripheral radially disposed slots and are cooperative with granular material hoppers to collect and transfer measured quantities of material into registry with cavities between axially spaced plug members rectilinearly advanced by a conveyor. To the extent that such rotative collector-transfer members are used in such known transfer arrangements for the filling of cavities having volume limits defined by the spacing of plural end plug members, such arrangements evidently demand extensive care in the placement of end plug members. In addition, these arrangements are considered to present a complex registration problem as between a rigid rotative member and a resilient conveyor. Furthermore, to the extent that material transfer is positively assisted in the former of these patents, the same is effected only upon dispensing and by a mechanical agency susceptible to binding where the granular material is a fine thermoplastic powder.
In another presently known arrangement, shown in U.S. Pat. No. 3,603,058, granular material is transferred to a vertically extending cavity formed by filter wrap and one end plug member therefor with the opposed end plug member being then inserted in the wrap atop the contained material. While this arrangement avoids the disadvantages above discussed by eliminating the need for careful spacing of end plug members prior to material transfer, the metering of material prior to its transfer is accomplished through a metering chamber having a cyclically displaceable closure member. Thus, the closure member defines a removable floor for the metering chamber to control transfer quantity, and mechanism is required for displacing such floor to dispense material to the filter wrap cavity. Furthermore, to the extent that this system contemplates positive material transfer, the same involves an air pressure assist operative during material dispensing only.